A transmission system, for example, is a broadband distribution network which is known from H. Hessenmuller et al., "Access Network Structures for Interactive Videoservices, " Part 1, Der Fernmeldeingenieur, Vol. 48, August 1994. An overview of broadband distribution networks is provided therein, which are also called BK [broadband cable] networks. In a higher-order BK repeater station, all television and radio programs are combined into a consistent program transmission and distributed to the user's BK repeater stations which are normally located in local exchanges. The television and radio programs are distributed in a downstream direction from the BK repeater stations to the subscribers.
A BK network of this kind represents a public network which terminates at tap devices which are also identified as in-house tap points. One or more subscriber terminals can be connected by means of a private, in-house network to each tap device, which are normally located in one building.
In order to create the possibility of interactive services, i.e., so-called Service-on-Demand (SoD) services, such as Video-on-Demand (VoD), in a BK network, in addition to the unidirectional services in the downstream direction (television and radio signals), return channels for signal transmission are provided in the upstream direction in a BK network. Thus, subscribers can send useful data to the SoD processing center, for example, to request information. The subscriber terminals have supplemental devices for interactive services; these supplemental devices are also called Set-Top Boxes.
A frequency range of about 5-30 MHz is specified for the return channels (upstream signals) and a frequency range about 40-300 MHz (450 MHz, hyperband) is specified for the television and radio signals (downstream signals) for existing BK networks.
The private, in-house network is exposed to numerous interferences, which are caused, for example, by shortwave radio transmitters, amateur radios and electric machines. In addition, the cables of the in-house network are sometimes designed without regard for such sources of interference. The upstream signals, in particular, are disturbed by these interferences. This problem is known, e.g., from N. De Muynck et al., "CATV-cables, they can do more!", International Television Symposium, Montreux, Switzerland, Jun. 15, 1991, pp. 179-195.